1. Field of the Invention
The present invention relates to an image pickup apparatus and a radiation image pickup apparatus which are used for a medical X-ray camera, an analyzing apparatus, a nondestructive testing apparatus, and the like.
2. Related Background Art
In recent years, in the medical X-ray camera, an image pickup system using a film is rapidly shifting to a digital image pickup system. The digital image pickup system enables image processing, so that diagnostic accuracy can be improved. In addition, because it is unnecessary to develop a film, an image taking interval can be shortened, with the result that image taking can be efficiently conducted on a group medical examination or the like.
An image pickup apparatus of the digital image pickup system includes an indirect system in which a radiation such as an X-ray is frequency-converted into light (for example, visible light) and the light is converted into an electrical signal such as a charge and a direct system in which a radiation is directly converted into an electrical signal such as a charge. In the indirect system, a wavelength converting layer (for example, a phosphor layer) that converts the radiation into the visible light, a photoelectric conversion element, and a thin film transistor (TFT) constitute a set and a plurality of such sets compose the image pickup apparatus. In addition, the direct system, a radiation image pickup apparatus and a TFT becomes a set and a plurality of such sets compose the image pickup apparatus.
For example, a structure in which a TFT including a first semiconductor layer is formed on a substrate and a semiconductor conversion element including a second semiconductor layer is formed thereon is described in U.S. Pat. Nos. 5,498,880 B and 5,619,033 B.
Up to now, in order to obtain a size and a resolution which are equal to those of a film, a radiation image pickup apparatus in which several millions of pixels each measuring several hundreds of microns in square in size are arranged on a substrate and which has a high definition and a large size of several tens of centimeter square is used for such a medical X-ray camera of the digital image pickup system.
In steps of manufacturing the image pickup apparatus, a defect such as a wiring short circuit or a disconnection, resulting from the presence of a particle or a process trouble is caused with some probability. Therefore, in addition to a production step control and a process development which are conducted for reducing a defect to be caused, the image pickup apparatus is manufactured using a repair technique for repairing a defect portion.
For example, a repair technique in which a defect pixel is irradiated with laser light to melt a metal and a semiconductor layer, thereby electrically cutting the defect pixel is disclosed in U.S. Pat. No. 6,332,016 B. Various cut portions such as a TFT region, a TFT drive wiring, a source or drain electrode, a signal wiring, or a bias wiring are considered according to a type of each defect. Note that, coordinate data of the electrically cut pixel is stored in a system of the digital X-ray camera and image processing for data interpolation is generally conducted using surrounding pixel data.
In general, according to the repair technique using the laser light, if a plurality of metallic films are located in a laser irradiation region, those metallic films are short-circuited in melting in some conditions. Therefore, there is the case where the defect portion is difficult to repair. In particular, according to the structure described in U.S. Pat. No. 5,498,880 B or U.S. Pat. No. 5,619,033 B, a lower electrode of a light detection element is located above the TFT region to be repaired. Therefore, if the repair is conducted, the electrodes or the wirings that compose the TFT and the lower electrode of the light detection element are short-circuited, so that it is difficult to electrically separate the defect portion from a pixel portion.
Also, if the metallic film or the semiconductor layer of a thick film having a high resistance is located above the wiring to be cut, there is a fear that a problem is caused in that cut processing precision is reduced or cutting cannot be performed in some cases.
As described above, in the case where the semiconductor layer of a switching element is different from the semiconductor layer of the semiconductor conversion element, it is required to make more extensive studies on a structure used for suitable repair.